The present invention relates to slow release liquid drug delivery devices.
It is known to provide an implantable device which delivers a drug slowly over a period of time. This approach avoids problems of patient compliance, and provides particular advantages where delivery of a drug to a specific target location allows use of much lower overall dosage than would be required for systemic delivery, possibly avoiding undesirable side effects.
In most cases of implantable drug delivery devices, a first surgical procedure is required to implant the device and then another surgical procedure is required to remove the device. Examples of implantable devices for delivery of liquid drugs include, but are not limited to, U.S. Pat. Nos. 5,163,920, 4,428,397, 4,820,273, 5,061,242, 5,993,414, 6,183,461 and 5,836,935.
Notably, U.S. Pat. No. 5,993,414 highlights particular problems encountered when trying to achieve reliable and leak proof weld joints between components.
In order to avoid the need for a second surgical procedure to remove the device, resorbable devices have been proposed. Such devices are generally limited to structures in which the drug is dispersed in a matrix of resorbable material and is gradually released as the matrix breaks down in the body. Examples of this approach may be found in U.S. Pat. Nos. 4,351,337 and 4,450,150 to Sidman. Although this approach has potential advantages, it does not achieve highly uniform drug release rates, and is not suitable for drugs which must be delivered in a liquid form or which have high diffusion rates through the matrix materials.
There is therefore a need for an implantable drug delivery device which would deliver a liquid drug over an extended period at a relatively constant rate without requiring surgical removal of the device after use.